The inventive concept relates generally to a hetero junction field effect transistor and to a method for manufacturing the same; and, more particularly, the inventive concept relates to a hetero junction field effect transistor that comprises a compound semiconductor and to a method for manufacturing the same.
Recently, communication techniques for high speed and high capacity signal transmission have been rapidly developed with the rapid development of info-communication fields. In particular, as the demands for personal portable phones, satellite communications, military radar, broadcasting communications, and repeaters for communications have grown in wireless communication fields, so too have the demands for the high speed and high power electronic devices, that are key components in high speed info-communication systems of microwave and millimeter-wave bands, increasingly grown.
A hetero junction field effect transistor (HFET) is representative of such a high power electronic device. The HFET is also called ‘a high electron mobility transistor (HEMT)’. The HFET may be used in fields using a high voltage, so that it may advantageously have a high breakdown voltage. A size of the HFET may be reduced while the HFET has a great power density. A semiconductor having a wide band gap (e.g., a compound semiconductor) may be used in fabricating the HFET in order that the HFET has the desired high breakdown voltage. Additionally, the HFET may advantageously have high heat conductivity. Accordingly, a cooling system for the HFET may be reduced in size. Moreover, the HFET may also advantageously have a larger saturated electron drift velocity. Thus, the HFET may better perform a high speed operation such as a high speed switching operation. For example, the HFET may have a higher operating frequency.
An electron mobility of silicon, as generally used in semiconductor devices, is too low to cause a high source resistance. Thus, research is being conducted for techniques of applying semiconductors based on III-V group compounds to the fabrication of HEMT structures. In particular, a gallium nitride-based compound has a relatively wide band gap, a high electron saturation velocity, and high chemical stability. Thus, the gallium nitride-based compound is attractive as a material for the fabrication of an HEMT. Research is also being conducted on techniques of using transistors based on such gallium nitride compounds in high temperature, high power, and high frequency electronic devices.